The present volume of the Gmelin thorium series describes the solid thorium-carbon compounds with the exception of the carbides and coordination compounds of the type 4 ThAn* X B, where B is a neutral ligand. The complex equilibria of the Th + ion with C-containing complexing agents are treated in the ThD1 volume. A first look into this volume demonstrates that a very large number of ThlV complexes has 4 been prepared. This may be explained by the fact that the Th + ion is the largest tetravalent ion of the periodic table. Therefore, the preparation of complexes with, e. g. , multidentate ligands can give a well-established picture of the coordination number as a function of charge and ionic radius. However, there are very few modern and updated comprehensive treatments of such data. Many compounds described in this volume are characterized by no other means than analytical composition and IR spectra (whereby IR spectra of organic ThlV salts mostly give information only on the ligand). Besides thorium carbonate and carbonato complexes, which are relevant for the environmental behaviour of this radioactive element and some organic complexes like oxalates, which are used in the field of analytical and separation chemistry nearly all other compounds described here are practically only of scientific interest. On the other hand in order to have scientifically reliable data, a very large part of these compounds needs further investigation and characterization.

Alloys of Uranium with Alkali Metals, Alkaline Earths, and Elements of Main Groups III and IV. The description of uranium and its compounds, for which the Gmelin Institute has started a series of volumes supplementing the main volume of 1936, follows in its arrangement closely the order chosen for the transuranium volumes. Part A treats "The Element," Part B "The Metal and its Alloys," Part C "The Compounds," Part D "The Chemistry in Solution," and finally Part E "The Coordination Compounds." Part E, "The Coordination Compounds" comprises two volumes which already have been finished and are available - completely written in English. Series A comprises 7 volumes which are all available. Series C will comprise 14 volumes of which only volume 6 is missing. Series D consists of 4 volumes dealing with the chemistry in solution, which already have been finished and are available. The present volume describes the alloys and the intermetallic compounds with the metals of main groups I to IV - those systems with semimetals such as boron and germanium are to be found in corresponding volumes in Uranium C series. In the volume B 2 main emphasis is given to the binary systems. The most frequently investigated systems are uranium-beryllium and uranium-aluminium because of their special scientific (U-Be) and technological (U-Al) importance.

The 3rd supplement continues the updating of the original 20 volumes on boron compounds published between 1974 and 1979. The first supplement consisting of 3 volumes covered all the literature uniformly up to the end of 1977, whereas the two volumes of the 2nd supplement have extended the literature coverage of boron compounds to 1980 and the four volumes of the 3rd supplement to 1984. The present volume continues the description of boron compounds with halogens, presenting those with chlorine, bromine and iodine. The compounds with chalcogens are completed here along with those of boron with S, Se, Te and Po. The final chapter on carboranes contains the carboranes themselves, together with metallacarboranes, and in the last section a description of carborane-containing polymers, mostly derived from the three isomeric dicarbadodecarboranes. Volume 4 of the 3rd supplement brings this supplement series to an end. It will be supplemented by a separately appearing index volume, which contains all the boron compounds dealt with in volumes 1 - 4 of this supplement series.

The present volume, Thorium C5, deals with the compounds of thorium and sulfur, selenium, tellurium, and boron, as well as with oxoacid compounds of the three chalcogen elements. Thorium borates have already been treated in Thorium C2. In contrast to the corresponding compounds of uranium the thorium sulfides, etc. , do not show any nuclear or other technological application; they are only of academic interest, despite some very interest ing electronic properties, especially of the 1 : 1 compounds. The thorium-sulfur and the thorium boron systems in particular were studied in detail, so that we have a clear picture of them, whereas there are still a lot of open questions in the systems Th-Se and Th-Te - not very different from other metal chalcogenide systems. Thorium sulfates are of some technological importance because they are formed in solution during recovery of thorium from monazite by sulfuric acid leaching. The very detailed and critical treatment of the chemical and physical properties of the compounds discussed also enables us to find gaps still remaining in our knowledge and thus to initiate new research in this field. I want to thank the two authors, Dr. Horst Wedemeyer (Karlsruhe) and Dr. David Brown (Harwell), for their excellent contributions, the "Literaturabteilung" of the Karlsruhe Nuclear Research Center for its help in providing reports and other documents difficult to procure, as well as the staff of the Gmelin-Institute, especially to Dr. K. -C.